Chances of getting pregnant each cycle and how long it takes

The chance of pregnancy in one cycle is about 1 in 4 at its peak

The American College of Obstetricians and Gynecologists (ACOG) puts the chance of pregnancy in any single menstrual cycle at around 1 in 4 for healthy couples in their 20s and early 30s (ACOG, 2023). Its guide to evaluating infertility gives the same range as 25 to 30 in 100 (ACOG, 2020, reviewed 2026). StatPearls, a peer-reviewed clinical reference, cites population studies with a lower average of 15 to 20 in 100 per month, and attributes the lower figures in the general population to age, undiagnosed infertility in either partner, obesity, smoking and other conditions that reduce fertility (Adebisi and colleagues, StatPearls, 2026).

Timing within the cycle matters. The American Society for Reproductive Medicine (ASRM) defines the fertile window as the six days ending on the day of ovulation, and in a study of 221 women it cites, the chance of pregnancy was highest when intercourse took place within the two days before ovulation (ASRM, 2022). Sex earlier in the cycle, even during a period, carries a much smaller chance; the guide to can you get pregnant on your period gives the figures.

Most couples conceive within a year of trying

Because every cycle carries its own chance, the cumulative figures say more than any single month:

• About 30 to 40 in 100 couples conceive within 3 months, and about 85 in 100 within 12 months (StatPearls, 2026).
• About 80 in 100 conceive within the first 6 months (ASRM, 2022).
• More than 80 in 100 couples in which the woman is under 40 conceive within a year, and about half of the rest conceive during the second year, which takes the total above 90 in 100 (National Institute for Health and Care Excellence, NICE, 2026).

These estimates come from different study populations, which is why they do not line up exactly. ASRM adds that the chance per month is highest in the first 3 months of trying and declines gradually after that (ASRM, 2022). For couples who have been trying for more than 3 years, the NHS puts the chance of a natural pregnancy in the following year at 1 in 4 or less (NHS, 2023). For what to do in that year, see how to get pregnant.

The average time to pregnancy is about 4 months among people who conceive

Two large data sets give almost the same average. In an analysis of 8,835 users of the Ovia Fertility app who started trying in 2015 and conceived within 12 months, the average time to conception was 3.94 months (Bradley and colleagues, Human Fertility, 2021). A reader survey run by the economist Emily Oster at ParentData, covering 32,414 pregnancies conceived while trying, found an average of 3.9 months (ParentData, 2022).

Both figures describe people who became pregnant and leave out everyone who did not, so neither is the average for everyone who tries; ParentData makes the same point about its own figure. The app study counted only conceptions within 12 months, and the ParentData survey was a convenience sample of its readers that excluded IVF. They are a fair guide to how long it takes to get pregnant for most people who conceive without treatment.

Regular cycles were linked to a shorter time to pregnancy

In the Ovia analysis, women with cycles of 27 to 29 days conceived sooner than women with shorter or longer cycles, and women whose cycle length varied by less than 9 days conceived about 0.7 months sooner than women with more variable cycles (Bradley and colleagues, 2021). This is an observational finding in app users, and it does not show that changing the cycle would change the time to pregnancy.

The chances fall with age, and faster from the mid-30s

By age 40, ACOG puts the chance of pregnancy at around 1 in 10 per cycle (ACOG, 2023). Over a full year the gap is smaller: in data that NICE reproduces, 92 in 100 women aged 19 to 26 were pregnant after 12 cycles, compared with 82 in 100 women aged 35 to 39 (Dunson and colleagues, 2004, in NICE, 2026). Those figures assume intercourse twice a week. The guide to age and fertility sets out the figures by age.

US and UK guidance recommend an evaluation after a year of trying, and sooner with age

ACOG recommends an infertility evaluation after 1 year of regular sex without birth control, after 6 months for women older than 35, and a conversation with an ob-gyn straight away for women older than 40 (ACOG, 2020, reviewed 2026). In the UK, NICE recommends assessment after 1 year, and referral to a specialist at the first appointment from age 36 (NICE, 2026). The details are in when to see a doctor about fertility.